// private property  
const _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";  

// public method for encoding  
export function encode(input) {  
    var output = "";  
    var chr1, chr2, chr3, enc1, enc2, enc3, enc4;  
    var i = 0;  
    input = _utf8_encode(input);  
    while (i < input.length) {  
        chr1 = input.charCodeAt(i++);  
        chr2 = input.charCodeAt(i++);  
        chr3 = input.charCodeAt(i++);  
        enc1 = chr1 >> 2;  
        enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);  
        enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);  
        enc4 = chr3 & 63;  
        if (isNaN(chr2)) {  
            enc3 = enc4 = 64;  
        } else if (isNaN(chr3)) {  
            enc4 = 64;  
        }  
        output = output +  
        _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +  
        _keyStr.charAt(enc3) + _keyStr.charAt(enc4);  
    }  
    return output;  
}  

// public method for decoding  
export function decode(input) {  
    var output = "";  
    var chr1, chr2, chr3;  
    var enc1, enc2, enc3, enc4;  
    var i = 0;  
    input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");  
    while (i < input.length) {  
        enc1 = _keyStr.indexOf(input.charAt(i++));  
        enc2 = _keyStr.indexOf(input.charAt(i++));  
        enc3 = _keyStr.indexOf(input.charAt(i++));  
        enc4 = _keyStr.indexOf(input.charAt(i++));  
        chr1 = (enc1 << 2) | (enc2 >> 4);  
        chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);  
        chr3 = ((enc3 & 3) << 6) | enc4;  
        output = output + String.fromCharCode(chr1);  
        if (enc3 != 64) {  
            output = output + String.fromCharCode(chr2);  
        }  
        if (enc4 != 64) {  
            output = output + String.fromCharCode(chr3);  
        }  
    }  
    output = _utf8_decode(output);  
    return output;  
}  

// private method for UTF-8 encoding  
 function _utf8_encode(string) {  
    string = string.replace(/\r\n/g,"\n");  
    var utftext = "";  
    for (var n = 0; n < string.length; n++) {  
        var c = string.charCodeAt(n);  
        if (c < 128) {  
            utftext += String.fromCharCode(c);  
        } else if((c > 127) && (c < 2048)) {  
            utftext += String.fromCharCode((c >> 6) | 192);  
            utftext += String.fromCharCode((c & 63) | 128);  
        } else {  
            utftext += String.fromCharCode((c >> 12) | 224);  
            utftext += String.fromCharCode(((c >> 6) & 63) | 128);  
            utftext += String.fromCharCode((c & 63) | 128);  
        }  

    }  
    return utftext;  
}  

// private method for UTF-8 decoding  
 function _utf8_decode(utftext) {  
    var string = "";  
    var i = 0;  
    var c = 0;
    var c1 = 0;
    var c2 = 0;  
    while ( i < utftext.length ) {  
        c = utftext.charCodeAt(i);  
        if (c < 128) {  
            string += String.fromCharCode(c);  
            i++;  
        } else if((c > 191) && (c < 224)) {  
            c2 = utftext.charCodeAt(i+1);  
            string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));  
            i += 2;  
        } else {  
            c2 = utftext.charCodeAt(i+1);  
            c3 = utftext.charCodeAt(i+2);  
            string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));  
            i += 3;  
        }  
    }  
    return string;  
}  
